This invention relates to methods and apparatus for communicating via a communication network, and more particularly to methods and apparatus for efficiently and economically communicating via a public network utilizing a shared account.
Public networks offer specialized, low-cost communication modes for the delivery of small packets of alarm and status information such as from remote industrial facilities. For example, networks operating in the Advanced Mobile Phone Service (AMPS) cellular network provide such communication modes via a cellular control channel, while networks operating in the Personal Communications Service (PCS) and Global System for Mobiles (GSM) offer Short Messaging Services (SMS) or equivalent services. Small data packets from remote terminal units (RTUs) are delivered via the low cost communication modes utilizing a sessionless, store-and-forward protocol. The maximum message length permitted by the protocol varies from system to system, but is typically equivalent to between 14 and 256 alphanumeric characters. Typical uses for SMS protocol in an industrial setting include the communication of alarm signals, switch closures, and event counts to a central computer via the network.
Occasionally, it is necessary in some applications to communicate more voluminous amounts of data to or from an RTU than can be efficiently handled using these low-cost communication modes. This need may arise, for example, hen an event logging function associated with an RTU is to be reprogrammed, or when a data history of a dynamometer associated with an RTU is to be uploaded to a central computer. In such cases, the need for wider bandwidth could be fulfilled by the RTU resorting to a switched connection protocol, e.g., placing a regular cellular or PCS call, to more rapidly and efficiently communicate larger data volumes. However, to be permitted to place a regular cellular or PCS call, a cellular or PCS subscriber account agreement is required. All such subscriber agreements have heretofore involved a monthly fee arrangement, the cost of which has hampered the development and spread of remote data collection applications. Network carriers have, in some instances, discounted the monthly cost of the service, but to date have still required an account for each RTU in a system. Where large numbers of RTUs need access to switched connection services for high volumes of data only occasionally, a large number of monthly service fees must be paid.
It would thus be desirable to provide methods and apparatus for utilization of low volume, low cost network data communication modes when feasible, and efficient and low cost use of high volume network data communication mode in systems in which the latter mode is infrequently required, in systems with multiple RTUs.
In one embodiment of the invention, a communication system is provided that has a plurality of remote terminal units (RTUs) that communicate via a network using a sessionless protocol and a switched connection protocol. RTUs communicate with a centralized server via the network. Short messages are communicated between the RTUs and the server utilizing the sessionless protocol. Examples of suitable sessionless protocols are cellular control channels, and the SMS protocol provided by GSM and PCS, or equivalent protocols in other systems. To communicate longer messages, the RTUs are configured to use at least one account identifier in a coordinated manner to communicate the longer messages via a switched connection protocol of the network.
In another embodiment of the invention, an RTU is provided that is configured to communicate data via a network using both a sessionless protocol and a switched connection protocol. The RTU is also configured to identify itself to the network using a first account identifier when communicating via the sessionless protocol, and to use a second account identifier different from the first account identifier when communicating via the switched connection protocol. In one embodiment of the RTU, the second account identifier is a shared account identifier identified by a server via the network, using the lower cost sessionless protocol.
In yet another embodiment of the invention, a method of operating a communication system including a plurality of remote terminal units communicating via a network is provided. Each RTU identifies itself to the network utilizing a unique account identifier to communicate in a first communication mode, and each RTU identifies itself to the network utilizing at least one shared account identifier to communicate in a second communication mode. The use of the shared account identifier is coordinated by a centralized server. In one embodiment, the first communication mode is a sessionless protocol mode, and the second communication mode is a switched connection protocol mode.
In still another embodiment of the invention, a server is provided for controlling access by a plurality of RTUs to a network. The server is configured to communicate commands to an RTU to conduct a switched connection protocol session via the network. The server is also configured to assign a shared network account identifier to the RTU for switched connection protocol access to the network and to coordinate usage of the shared network account identifier among the plurality of RTUs. A corresponding method of operating a server is also provided.
It will be seen that the various embodiments of the invention provide users of low cost modes of public communication networks to economically deploy large, widely dispersed, low-volume data networks while retaining a low-cost method for handling occasional high-volume data transfers.